McMaster-Carr, look up screws, bolts or some other type of hardware. Pick one at random and you will notice a 'CAD' tag pop up for the item. Click and and download a CAD file of the item. Now open your modeling program and import it. Nice. You now have mechanically accurate parts to detail stuff with or to use as a guide for designing real-life parts. That's what I have been doing. I downloaded the exact screws I wanted for the iris and used them to size the holes and tracks correctly. I've been using IGS files successfully in C4D.
This is also great for my fellow MakerBots out there. You can take this file and print plastic screws. PLASTIC SCREWS! They don't have CAD files for everything, but there's still plenty.
Also, McMaster-Carr is the most awesome place in the world. Their catalog is about 6" thick. When I order something, it's here the next day with standard shipping. If you want to learn about rubber, plastic or static eliminating blowers, this is the place to go. Each section has an 'About' preface that will give you a good primer on hardware. If you email customer service, you will hear back from them in less than an hour. It's like Christmas.